With the development of communication devices and technologies, there is a need for services for providing and sharing information. Recently, the smartphone and tablet Personal Computer (PC) make it possible for a user to acquire and share information through a wireless communication system. However, in order for the user to acquire and share the information through the wireless communication system, there is a need for a communication infrastructure. Also, the wireless communication system is not efficient at exchanging trivial but useful information of the type used in everyday life due to system complexity and time delay.
Thus, the Device to Device (D2D) service has been introduced to make it possible for the devices to share device information to establish a communication link for direct communication without a legacy communication infrastructure.
In the D2D wireless communication, a device acquires synchronization with adjacent devices. Afterward, the device performs device discovery at a predetermined time using a predetermined resource to acquire the information on the devices discovered. Here, the device information may include device identity information, interest, and application information.
As described above, the device supporting D2D wireless communication discovers the adjacent devices using the predetermined resource at the predetermined discovery period. That is, the device receives the device information broadcast by adjacent devices on the predetermined resource in the predetermined discovery period to discover the adjacent devices. The device also broadcasts its device information on the predetermined resource in the discovery period in order for other devices to discover it.
Typically, the device discovery and device information broadcast procedure is performed in periodic device discovery period. There is a related-art method in which the device, when lacking in transmit power, sends the discovery signal in the device discovery period occurring at a long interval and, between the device discovery periods, the base station transmits the discovery signal instead of the device.
FIG. 1 is a diagram illustrating a device discovery mechanism according to the related art.
Referring to FIG. 1, the terminals A, B, and C are synchronized with the base station. As shown in part (a) of FIG. 1, the terminal A is the device operating with a normal transmit power and a relatively short discovery signal transmission interval 103. As shown in parts (b) and (c) of FIG. 1, the terminals B and C are devices experiencing power shortage and thus operating with relatively long discovery transmission intervals 105 and 107. At this time, the base station transmits the discovery signals 109 and 111 of the terminals B and C in the discovery signal-off duration between the discovery durations of the terminals B and C instead of the terminals B and C.
At this time, the base station transmits the discovery signals using the same resource as the corresponding device in the discovery signal off-duration.
FIG. 2 is a diagram illustrating a resource structure in a device discovery period according to the related art.
Referring to FIG. 2, the device selects the resource 201 in the discovery signal transmission duration to transmit the discovery signal. Before the next discovery signal transmission duration, the base station transmits the discovery signal instead of the device on the same resource 203 and 205 allocated to the device. If the next discovery signal transmission duration arrives, the device transmits its discovery signal on the resource 207.
In the related-art technology, the base station transmits the same discovery information using the same resource 203 and 204 as the terminal. At this time, the resource 201 selected by the terminal may not be used by the base station due to a resource collision. Also, the related-art technology has a drawback in that the device discovery ranges of the terminal and the base station mismatch due to the different transmission points in searching for adjacent devices and the link distance determination based on the received signal may cause error.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.